Such an incremental displacement transducer is e.g. known from DE 197 01 319 A1 and has a scanning unit linked or to be linked with the first object for scanning a division or spacing track linked or to be linked with the second object having first areas and second areas, which are arranged in period length-alternating manner. The first areas have a first physical property and the second areas a second physical property differing therefrom. The scanning unit also has a plurality of sensors for scanning the first and second areas on the basis of the first and/or second physical property. Finally, there is an evaluation unit linked with the scanning unit for determining the displacement on the basis of measuring signals of the sensors.
With such a method, also known from DE 197 01 319 A1, a spacing track linked with the first object is scanned with a plurality of sensors linked with the second object. The spacing track has first areas with a first physical property and second areas with a second physical property, which are arranged in period length-alternating manner and from the measuring signals of the sensors obtained as a result of the first and/or second physical property, the displacement of the first object relative to the second object is determined.
Inductive incremental displacement transducers are also described in DE 31 00 486 A1, EP 1 071 927 B1, U.S. Pat. No. 4,893,078 and U.S. Pat. No. 5,003,260.
Incremental displacement transducers are used for measuring position changes. Two mutually spaced sensors in each case determine the position of one spacing track. By counting the single pulses the movement of the spacing track relative to the sensors can be determined. As the signals generated by the two sensors have a phase shift of e.g. 90°, a direction identification is also possible.
If inductive sensors are used in the case of the incremental displacement transducer, difficulties arise due to the dependence of the switching point of the sensors on laterally approaching a metal object, e.g. a conductive area of the spacing track, on the distance of the sensor from said spacing track. The closer the conductive area of the spacing track is to the sensor, the earlier it is identified.
Thus, the 1:1 pulse pause ratio desired for direction identification can only be obtained for a very specific spacing or distance.
Moreover, in the prior art spacing tracks are always necessary, where the first and second areas always have the same extension. Thus, spacing tracks in most cases must be separately applied to the objects to be monitored, even if there are already repetitive structures, which would fundamentally be suitable for identifying a shift.
The object of the invention is to provide an incremental displacement transducer and a method for determining the displacement of a first object relative to a second object where, substantially independently of the specific distance from the sensors used to a spacing or division track and substantially independently of the specific spacing track used, reliable measurement results are provided.
Advantageous further developments of the inventive incremental displacement transducer form the subject matter of the dependent claims and are also described in the following description, particularly in conjunction with the drawings.